The present invention relates to a resin composition comprising a graft copolymer alone or a mixture of the graft copolymer and a thermoplastic resin compatible therewith, the graft copolymer having been obtained by graft-polymerizing a vinyl or vinylidene monomer onto a rubber trunk polymer with low electrical resistance comprising 1 to 50% (by weight, as in all percentages and parts set forth hereinafter) of a monomer comprising 4 to 500 alkylene oxide groups and a conjugated diene and/or an alkyl acrylate, which graft copolymer possesses an antistatic property that is not practically lowered by washing.
In general, plastics have high electrical resistance and tend to be easily charged with static electricity due to friction or peeling. For this reason, plastics are liable to attract dust and dirt, resulting in various troubles such as impairment of the appearances of shaped articles, sheets, films and fibers formed from these plastics.
Method for imparting antistatic property to such plastics that are susceptible to static electricity have been investigated and can be roughly classified as follows.
1. Methods which involve kneading an antistatic agent into the plastics.
2. Methods which involve applying an antistatic agent (surfactant) over the surface of the plastics.
3. Methods which involve applying a silicone compound over the surface of plastics.
4. Methods which involve chemically reforming the molecular structure of plastics.
Of these methods, a method which involves kneading an antistatic agent into plastics cannot successfully impart a permanent antistatic effect, and, when the antistatic agent present over the surface of the plastics is removed by washing with water or rubbing, the antistatic effect is lost.
As an exception, an antistatic agent of kneading-in type possessing an antiwashing property suitable for use in polyethylene, polypropylene and polyvinyl chloride has been reduced to practice. However, this antistatic agent is accompanied by certain problems. One is that a considerable time is required until its antistatic effect is restored after washing. Another is that, if an antistatic agent bleeds excessively over the surface of plastics, dust and dirt adhere thereonto. Still another problem is that a satisfactory antistatic agent has not yet been obtained for transparent and hard plastics on a commercial basis. Furthermore, this method requires a step of kneading-in an antistatic agent.
If the method which involves applying an antistatic agent over the surface of plastics is employed, its antistatic effect is drastically impaired upon washing.
The method which involves applying a silicone compound over the surface of plastics provides an excellent and substantially permanent antistatic effect but is disadvantageous from the standpoint of process efficiency and economy.
The method which involves chemically reforming the molecular structure of plastics by introducing hydrophilic groups into plastics by polymerization and the like generally requires the introduction of a considerable quantity of hydrophilic groups in order to obtain a high antistatic effect, so that the mechanical and other properties of the plastics deteriorate because of the increased hygroscopicity thereof.